2-(Phenylhalonium)-4,5-dicyano-2H-imidazole ylids

ABSTRACT

Pyrolysis of 2-diazo-4,5-dicyano-2H-imidazole in the presence of certain aryl halides yields 2-(arylhalonium)-4,5-dicyano-2Himidazole ylids. The ylids are intermediates in the preparation of 1-aryl-2-halo-4,5-dicyanoimidazoles.

United States Patent 11 1 Sheppard [4 1 Oct. 21, 1975 2-(PHENYLHALONIUM)-4,5-DICYANO-2I-l- IMIDAZOLE YLIDS [75] inventor: William Arthur Sheppard,

Wilmington, Del.

[73] Assignee: E. I. Du Pont de Nemours &

Company, Wilmington, Del.

[22] Filed: Dec. 4, 1973 21 Appl. No.: 421,597

UNITED STATES PATENTS 3,793,339 2/1974 Webster 260/309 OTHER PUBLICATIONS J.A.C.S. 95, pp. 26952697, (May 3, 1973), Sheppard et al.

Primary Examiner-Sherman D. Winters Attorney, Agent, or Firm-Anthony P. Mentis [57] ABSTRACT Pyrolysis of 2diaz0-4,5-dicyano-2l-l-imidaz0le in the presence of certain aryl halides yields 2- (arylhalonium)-4,5dicyan0-2H-imidazole ylids. The ylids are intermediates in the preparation of l-aryl-Z- halo-4,S-dicyanoimidazoles.

4 Claims, N0 Drawings 2-( PHENYLI-IALONIUM )-4,5-DICYANO-2I-l- IMIDAZOLE YLIDS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to 2-(arylhalonium)-4,5- dicyano-ZH-imidazole ylids and to the process of making them by pyrolysis of 2-diazo-4,5-dicyano-2H- imidazole in the presence of certain aryl halides.

2. Prior Art 2-Diazo-4,5-dicyano-2I-I-imidazole is described by Sheppard and Webster [1. Am. Chem. Soc. 95, 2695 (1973)]. Phenyliodonium methylene ylids are known [Karele and Neiland, J. Org. Chem. USSR 4, 1755 (1968); I-Iayasi et al., Bull. Chem. Soc. Jap. 43, 2506 (1970)]. A bromonium ylid has been suggested as an intermediate in the reaction of 2,5-di-tert-butylbenzene- 1 ,4-diazooxide with 2,6-diisopropyl-4- bromophenol [Pirkle and Koser, .I. Am.'Chem. Soc. 90, 3598 (1968)].

SUMMARY OF THE INVENTION The 2-(arylhalonium )-4,5-dicyano-2H-imidazole ylids of the invention have the formula wherein X is chlorine, bromine or iodine, and

R is aryl of 6-10 carbon atoms, any substituents on R being selected from the group consisting of bromine, chlorine, fluorine and iodine, and alkyl of l-4 carbon atoms.

The process of the invention involves pyrolysis of 2- diazo-4,5-dicyano-2H-imidazole (11) below in the presence of an aryl halide having the formula RX, where X and R have the foregoing values.

The reaction underlying the process can be illustrated as follows:

ylids (I) undergo rearrangement on heating with formation of 1-aryl-2-halo-4,5-dicyanoimida2oles (III). This reaction can be illustrated as follows:

(Ill) When the reaction of II and RX is prolonged or carried out at higher temperature, I is generally converted entirely to III.

Representative RX coreactants are chlorobenzene. bromobenzene, iodobenzene, p-chlorotoluene, l-fluoro-3-iodobenzene. l-chloronaphthalene, 2- bromonaphthalene, 7-bromo-l-methylnaphthalene, 1-chloro-2-fluoronaphthalene and 2-chloro-l.6-dimethylnaphthalene.

In the process of the invention the 2-diazo-4,5- dicyano-2H-imidazole must be at least partly soluble, i.e., in the liquid phase, at the temperature of the reaction. The RX coreactant can itself be the reaction medium, or a normally liquid organic solvent which is relatively non-reactive with the diazo compound can be used as the reaction medium. Suitable organic solvents include acetonitrile, dimethylformamide, dimethylacetamide and dimethyl sulfone. It is preferred to use the RX coreactant as the reaction medium.

The reaction can be carried out in the temperature range of about 0 to about 100., the range of to C being preferred.

The process can be carried out over a time schedule of from about one to about 24 hours, the appropriate specific time being generally dependent upon the temperature of reaction. The reaction time is generally shorter at higher temperatures since the rate of reaction increases as the temperature increases.

The process can be carried out at any pressure which provides liquid phase conditions for the reactants, the pressure usually and preferably being atmospheric pressure. However, commensurate with liquid phase conditions, any pressure below or above atmospheric pressure may be used if desired, a practical range being 0.01 to 5000 atmospheres.

SPECIFIC EMBODIMENTS OF THE INVENTION The following examples illustrate the invention and describe typical products obtained. Temperatures are given in degrees Centigrade and the reactions are conducted at atmospheric pressure. Reduced pressures, where indicated, are given in terms of millimeters of mercury. All parts and percentages are by weight unless otherwise stated.

EXAMPLE 1 2-(Phenylchloronium)-4,5-dicyano-2I-I-imidazole ylid A. Three separate mixtures each of 5.2 g (36.1 mmol) of 2diazo-4,5-dicyano-2H-imidazole and 250 ml of chlorobenzene were heated at 8588 for 1 hr. The combined effluent gases totaled 2.9 l The reaction mixtures were combined and diluted with 6 of petroleum ether. and the solution was cooled to 20C. The solid which precipitated was collected on a filter and then dissolved in dichloromethane. This solution was washed with aqueous sodium bicarbonate and the wash acidified and extracted with ethyl acetate to give 8.60 g (35% yield) of 2-(chlorophenyl)4,5- dicyanoimidaz'ole (2). The dichloromethanelayer was diluted with petroleum ether at room temperature, which caused 4.45 g (18% yield) of 2- (phenylchloronium)-4,5-dicyano-2H-imidazole ylid (1) to precipitate. An analytical sample was recrystallized from chloroform-petroleum ether; m.p. 120l2lC UV X 247 nm (614,000), 285 (3200).

Anal. Calc. for C H N CI: C, 57.8; H, 2.2; N, 24.5; Cl, 155 Found: C, 57.8; H, 2.2; N, 24.7; CI, 16.2.

B. In a similar single run at 80C. for 1.75 hours, 11 and excess chlorobenzene yielded 26% of (1), 50% of (2) and 21% of(3).

C. when the ylid l was refluxed in chloroform overnight, about 50% of it was rearranged to 2-chloro-lphenyl-4,S-dicyanoimidazble (3).

EXAMPLE 2 2-(Phenylbromonium)-4,5-dicyano-2H-imidazole ylid Reaction of bromobenzene with 2- EXAMPLE 3 2-( Phenyliodonium )-4,5-dicyano-2H-imidazole ylid A. 2-Diazo-4,5-dicyano-2H-imidazole= (11: 5.5g, 0.38 mole) was heated at C in 70 ml of'iodobenzene. After 6 hours, approximately the theoretical yield of gaseous nitrogen (91 0 ml was evolved. After refluxing overnight, the solution was filteredhot to give 109 g of a yellow powder that was recrystallized from acetonitrile. This product mp-221- 22'29C.; was characterized as the iodov ylid (4).by ir, nmr, elemental analysis and mass spectra.

Anal. Calcd for C H N ISC; 41.3; H, 1.57; N; 17.5;

I, 39.7 Found: C, 41.5;H, 1.79; N, 17.2; 1, 39.5413 1.72 H. The filtrate was evaporated to give 1 .4 of crystalline solid, mp about 55C., that appeared by ir and n'mr to be a mixture of. 2 -(iodophe'nyl)-4,5-dicyanoimi'dazole (5) and 1phenyl-2-iodo-4,5-dicyanoimidazole (6).(5) is believed to be an original coproduct with (4) and (6) to be derived by rearrangement of (4).

B. The iodo ylid.[(44), 1g]:was mixed with 30 ml-of o-dichlorobenzene and the latter heated-to boiling for 1.25 hours. The mixture was then filtered hot and the insoluble solid washed with petroleum ether to recover 0.14 g of unchanged ylid, identified by infrared analysis. Addition of more petroleum ether to the filtrate at room temperature precipitated an additional 0.34 g of the ylid starting material. The final filtrate yielded a residue which was recrystallized from hexane to yield about 0.1 g of (6), mp 150151, identified by mass spectral analysis.

Anal. Calcd for C H N I: C, 41.3; H, 1.57; N, 17.5 Found: C, 41.36; H, 1.76; N, 17.05

EXAMPLE 4 2-(p-Tolylchloronium)-4,5-dicyano-2H-imidazole Ylid 11 was reacted with p-chlorotoluene under conditions similar to those of Example 1. Products were isolated EXAMPLE 5 2-(m-Fluorophenyliodonium )-4,5 -dicyano-2H- imidazole Ylid Reaction of l-fluoro-3-iodobenzene with 11 by the procedure of Example 4 yielded 41.8% of 2-(mfluorophenyl-iodonium )-4,5-dicyano-2H-imidaz ole ylid (l: X =1, R =C H F, mp dec.), 4% of 2-iodol-(m-fluorophenyl)-4,5-dicyanoimidazole (111: X =1, R C H F), and 29.6% of base soluble 2-(2-fluoro-4- iodophenyl)-4,5-dicyanoimidazole.

Anal. (ylid) Calcd for C H FlN z C,.-39.08; H', 1.19; N, 16.57 Found: C, 39 .31; H, 1.34; N, 15.99.

The novel I 2-(arylhalonium)-4,5 dicyano-2H- imidazole ylids are useful as intermediates Ito 1- aryl-2- halo-4,5-dicyanoimidazoles. The 1-aryl-2-halo-4,5- dicyanoimidazoles are generally useful as agents for removing halogen acids, e.g., hydrogen chloride, from orwherein X is chlorine, bromine or iodine and R is phenyl or naphthyl, any substituent on R being selected from the group consisting of bromine, chlorine, fluorine and iodine, and alkyl of l-4 carbon atoms.

2. A compound of claim 1 where X is chlorine and R is phenyl.

3. A compound of Claim 1 where X is bromine and R is phenyl.

4. A compound of claim 1 where X is iodine and R is phenyl. 

1. A COMPOUND OF THE FORMULA
 2. A compound of claim 1 where X is chlorine and R is phenyl.
 3. A compound of Claim 1 where X is bromine and R is phenyl.
 4. A compound of claim 1 where X is iodine and R is phenyl. 